Variable area jet propulsion nozzles



March 13, 1962 J. M. s. KEEN VARIABLE AREA JET PROPULSION NOZZLES 2 Sheets-Sheet 1 Filed June 10. 1959 March 13, 1962 J. M. s. KEEN VARIABLE'AREA JET PROPULSION NOZZLES 2 Sheets-Sheet 2 Filed June 10. 1959 3,024,599 Patented Mar. 13, I962 VARIABLE AREA JET PROPULSION N OZZLES John Michael Storer Keen, Allestree, England, assignor to Rolls-Royce Limited, Derby, England, a British company Filed June 10, 1959, Ser. No. 819,456 Claims priority, application Great Britain July 14, 1958 7 Claims. (Cl. 60-35.6)

This invention comprises improvements in or modifications of jet nozzles of the variable area kind as described and claimed in patent specification Number 646,498.

According to patent specification Number 646,498 a jet nozzle for jet propulsion purposes comprises a tubular wall member defining a gas passage and having an outlet at one end, and at least one flap member which is adjustable between a first position in which it projects into the gas passage upstream of the nozzle outlet to define a first eliective area of the nozzle less than the area of said outlet of the tubular wall member, and a second position in which it is retracted and the nozzle has a second effective area greater than the first effective area, and the total peripheral extent of such flap members being a minor proportion of the total peripheral extent of the nozzle outlet.

According to the present invention in one aspect, in a jet propulsion nozzle as claimed in patent specification No. 646,498 the tubular wall has secured to it a series of angularly-spaced axially-extending structures which over at least the peripheral portion of the gas passage define a number of gas-flow channels such that in operation a silencing effect is obtained as compared with an equivalent plain nozzle, and the or each flap member extends circumferentially between a pair of said structures and in said first position the lateral edges of the flap member co-operate with adjacent circurnferent-ially-facing walls of the pair of structures to reduce the outlet area of the channel between them.

According to the invention in another aspect, in a jet propulsion nozzle as claimed in patent specification No. 646,498 the (or each) flap member is pivoted by its upstream end to the tubular wall member, and has pivoted to its downtsream end one end of a secondary flap member the other end of which is connected to power means by which movement of the flap members is effected, the secondary flap member forming in said first position a downstream-facing wall extending outwardly from said downstream end.

Preferably, the secondary flap has mounted on it at said other end roller means running in tracks which may be curved and are provided on fixed structure, the rollers and tracks being adapted to reduce the loads being transmitted from the flap to the power means. The power means i conveniently an axially-extending ram, whereof the operating piston is connected to the said other end of the secondary flap member by a link, and means is provided to limit radially-inward movement of the flap mernbers when the gas pressure in the nozzle is low or at zero.

Preferably, it is arranged that when the flap members are in the first position, the secondary flap member is loaded on its upstream-facing surface by pressure gas derived from the passage and on its downstream-facing surface by substantially atmospheric pressure, whereby the gas loads on the secondary flap member assist to maintain it in position. This may be achieved by providing a cut-out in the tubular wall member to receive the firstmentioned flap member when it is retracted and by providing a box structure externally of the tubular member to cover the cut-out and flap members, the box structure upstream of the secondary flap member when in the first position being open to the gas passage and downstream of the secondary flap member being open to atmosphere. In such an arrangement using a ram as above set forth, the ram piston may have an area open to the interior of the box structure. One advantage of this arrangement is that in the event of failure of the power supply to the ram when the flap members are in the second position, the gas pressure within the box structure will act on the piston to hold the flap members in position.

One embodiment of jet propulsion nozzle of' this invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 is a view on the outlet end of the nozzle,

FEGURE 2 is an external side view of the nozzle,

FiGURE 3 is a section on the line 33 of FIGURE 1 drawn to a larger scale, and

FIGURE 4 is a section on the line 4-4 of FIGURE 3.

The nozzle comprises a tubular wall 10 (FIGURES l and 2) which is frusto-conical with its larger end downstream, and a series of angularly-spaced hollow axiallyextending streamlined structures 11, say six structures, which divide the peripheral portion of the gas passage through the nozzle into a corresponding series of channels 12 so as to reduce the noise-level as compared with an equivalent plain convergent nozzle. The structures 11 are of such shape that the cross-section of the gas passage decreases in the direction of gas flow.

In order to reduce the outlet area of the nozzle during say take-off of an aircraft a pair of flap arrangements 13 are provided in a diametrically opposite pair of the channels 12, which flap arrangements are retractable to give a larger outlet area for cruise operation.

Each flap arrangement 13 comprises (FIGURE 3) a main flap 14 which is pivoted at its upstream end to the tubular wall member 10 and which extends from its pivot 15 downstream towards the outlet of the nozzle. The main flap 14 has a first position of adjustment shown in dotted lines in FIGURE 3 in which it projects into the channel 12 between the adjacent structures 11 and co-operates by its lateral edges 14a with the walls of the structures 11 to reduce the cross-section of the channel 12 (see FIGURE 1). The main flap 14 has a second position of adjustment shown in full lines in FIGURE 3 in which it occupies a cut-out 16 in the tubular wall member 10 and does not obstruct the channel 12. It will be seen that there is a substantial gap between the upstream edge of the flap 14 and the upstream edge of the cut-out 16.

Each flap arrangement also comprises a secondary flap 17 Which is connected at one of its ends through pivot 18 to the downstream end of the main flap 14. The other end of the flap 17 has mounted on it a pin 19 carrying a pair of rollers 20 (FIGURES 3 and 4) and these rollers co-operate with axially-curved channelled tracks 21 formed on the internal surface of a member 22 secured to the top of a box structure. Since the rollers 26; run in channels 21 any side load tending to cause lateral displacement of the flaps 17 will cause the rollers 29 to bear against the sides of the channels and in this way the fiap is supported against movement under the action of side loads.

The pin 19 also provides a pivotal connection between the flap 17 and a link 24 by which the flap 17 is connected to a ram piston 25 which works in a ram cylinder 26 which is secured at one end to a flange 27 on the tubular wall member 16' and at its other end to the box structure 23. The cylinder 26 has pressure fluid supply connections 28, 29 to it and a smaller diameter portion 26a open to the interior of the box structure 23. The piston 25 has an extension 25a which is slidable in a bush 26d located in the cylinder portion 26a and the extension 25a is hollow so as to permit angular movement of the link 24. The extension 25a also allows an area of the downstream face of the piston to be subjected to the pressure within the box structure 23. A sealing ring 2512 is provided between the upstream end of cylinder portion 26a and the extension 25a of piston 25.

The link 24 is formed with a hooked lug 3G (FIGURES 3 and 4) projecting into a stepped channel 31 which runs parallel with tracks 21, the lug 30 and channel 31 serving to prevent radially inward movement of the flap arrangements 13 when the gas pressure within the tubular wall is low or at zero.

The box structure 23 has a slot 32 in its downstream wall through which the interior of the box structure on the downstream side of the secondary flap 17 is in communication with atmosphere.

When the main flap 14 is moved into its first position (dotted lines in FIGURE 3) by feeding pressure fluid such as compressed air to cylinder space 2612, the secondary flap 17 extends radially outwards as shown in dotted lines in FIGURE 3 to form a downstream facing wall. Since gas can flow as indicated by arrow 33 from the gas passage of the nozzle into the box structure 23 on the upstream side of the flap 17 and the downstream side of the flap 17 is at substantially atmospheric pressure, the flap 17 has a resultant load on it tending to maintain it in position. In this position, the outlet area of the nozzle is a minimum.

To move the flaps 14, 17 to their second and retracted positions (full lines in FIGURE 3), pressure fluid is fed to cylinder space 260 and the piston 25 moves to the left. In this position of the flaps, flap 14 forms a smooth continuation of the tubular wall member 10 and flap 17 is housed in the box structure 23. If the pressure fluid supply to ram 25, 26 should fail, the gas load acting to the left on piston 25 due to the gas pressure Within the box structure 23 on the upstream side of the fiap 17 holds the parts in their full line positions.

I claim:

1. A jet propulsion nozzle comprising a tubular wall member defining a gas passage and having an outlet at one end, and at least one fiap arrangement which is adjustable between a first position in which it projects into the gas passage upstream of the nozzle outlet to define a first effective area of the nozzle less than the area of said outlet of the tubular wall member, and a second position in which it is retracted and the nozzle has a second effective area greater than the first effective area, power means for effecting adjustment of the flap arrangement, the fiap arrangement comprising a main fiap member extending longitudinally of the tubular wall member and pivoted by its upstream end to the tubular wall member, and a secondary flap member pivoted by one end to the downstream end of the main fiap member and pivotally connected by its other end to the power means, the secondary flap member forming in said first position a downstream-facing wall extending radially outwardly from said downstream end of the main flap member, the secondary flap member having first and second surfaces which in the first position of the flap arrangement face upstream and downstream respectively, means permitting the secondary fiap member to be loaded on its upstream-facing surface by pressure gas derived from the gas passage and on its downstreamfacing surface by substantially atmospheric pressure, whereby the gas loads on the secondary fiap member assist to maintain it in said first position.

2. A jet propulsion nozzle according to claim 1, comprising fixed structure externally of the tubular wall member, channelled tracks provided on fixed structure, roller means mounted on said other end of the secondary flap member and running in said channelled tracks, the rollers and tracks being adapted to prevent tangential loads being transmitted from the flap to the power means.

3. A jet propulsion nozzle according to claim 2, wherein the tracks are curved.

4. A jet propulsion nozzle according to claim 2, said power means comprising an axially-extending ram having an operating piston, a link connecting said piston to the said other end of the secondary fiap member, and means limiting radially-inward movement of the flap members when the gas pressure in the nozzle is low or at zero.

5. A jet propulsion nozzle according to claim 4, wherein the means to limit said radially-inward movement of the flap members comprises a hooked lug on the link and a stepped channel which runs parallel with the tracks, said hooked lug engaging in the stepped channel.

6. A jet propulsion nozzle comprising a tubular wall member defining a gas passage and having an outlet at one end, and at least one flap arrangement which is adjustable between a first position in which it projects into the gas passage upstream of the nozzle outlet to define a first effective area of the nozzle less than the area of said outlet of the tubular wall member, and a second position in which it is retracted and the nozzle has a second effective area greater than the first effective area, power means for effecting adjustment of the flap arrangement, the flap arrangement comprising a main flap member extending longitudinally of the tubular wall member and pivoted by its upstream end to the tubular wall member, and a secondary flap member pivoted by one end to the downstream end of the main flap member and pivotally connected by its other end to the power means, the secondary flap member forming in said first position a downstream-facing wall extending radially outwardly from said downstream end of the main flap member, there being a cut-out in the tubular wall member to receive the main flap member when the flap arrangement is retracted, and a box structure externally of the tubular member to cover the cut-out and flap arrangement, the secondary flap member when in said first position projecting radially into the box structure and dividing the interior of the box structure into upstream and downstream spaces, the space of the box structure upstream of the secondary flap member being open to the gas passage and the space of the box structure downstream of the secondary fiap member being open to atmosphere.

7. A jet propulsion nozzle according to claim 6, said power means comprising an axially extending ram having an operating piston, the ram piston having an area open to the upstream space of the box structure so that in the event of failure of the power supply to the ram when the flap members are in the retracted position, the gas pressure Within the box structure acts on the piston to hold the flap arrangement in said retracted position.

References Cited in the file of this patent UNITED STATES PATENTS 2,794,317 Brown June 4, 1957 2,928,234 Brown Mar. 15, 1960 FOREIGN PATENTS 165,369 Australia Sept. 26, 1955 558,987 Belgium Nov. 1, 1957 1,141,221 France Mar. 11, 1957 1,164,936 France May 19, 1958 

